Unless the regulations have changed in recent years (and I have to admit to
not being up to date on this), the principle used to be that no rechargeable
battery could be made of flameproof construction as the batteries must be
able to breathe. Cap lamp batteries were not of flameproof construction,
they were deemed to be safe because of the method of construction and use.
Likewise loco batteries were not of flameproof construction.
I do recall some photography being carried out underground in the 1950s and
60s using a power supply and lighting unit which was of flameproof
constructions. The complete unit was about 0.75 m x 0.75m x 0.75m and was
quite heavy, consequently it was not used very much. This may be the main
reason why there was not too much underground photography carried out in
safety lamp mines at that time.
Alan Vickers.
|